Department of Experimental Psychology.
Department of General Psychology, University of Padova.
Dev Psychol. 2014 Apr;50(4):986-93. doi: 10.1037/a0034678. Epub 2013 Oct 7.
Inversion effect in biological motion perception has been recently attributed to an innate sensitivity of the visual system to the gravity-dependent dynamic of the motion. However, the specific cues that determine the inversion effect in naïve subjects were never investigated. In the present study, we have assessed the contribution of the local gravity-dependent motion (i.e., the orientation of individual dot trajectories) and the global configuration (i.e., the vertical location of the dots representing the feet within the display) in determining the inversion effect for biological motion in humans at birth. Results showed that 2-day-old newborns, at their 1st exposure to point-light displays, preferred a biological motion stimulus representing the legs of a walking animal compared with an identical display in which individual dot trajectories were locally inverted so that the motion violates the gravity force (Experiment 1). Interestingly, the global configuration affected the analysis of the gravity-dependent profile of dots motion. Indeed, the spontaneous preference disappeared when the local dots representing feet were embedded in a more complex global display and all the dots representing feet were located on the ground below the rest of the body (Experiment 2). Finally, results revealed that the orientation of the global configuration per se is not a crucial factor in determining newborns' preference (Experiment 3). These results suggest that humans possess an inborn predisposition about the direction of the gravity force that imprints biological motion and supports the hypothesis that a mechanism for the detection of biological motion is already at work before visual experience.
生物运动知觉中的反转效应最近归因于视觉系统对运动的重力依赖动力学的先天敏感性。然而，对于天生的受试者，决定反转效应的具体线索从未被研究过。在本研究中，我们评估了局部重力依赖运动（即，单个点轨迹的方向）和全局配置（即，代表脚的点在显示器中的垂直位置）在确定人类出生时生物运动反转效应中的贡献。结果表明，在首次接触光点显示时，2 天大的新生儿更喜欢代表动物腿部运动的生物运动刺激，而不是代表腿部运动的相同显示，其中单个点轨迹局部反转，使运动违反重力（实验 1）。有趣的是，全局配置会影响对重力依赖点运动轨迹的分析。事实上，当本地代表脚的点嵌入更复杂的全局显示中，并且所有代表脚的点都位于身体其余部分下方的地面上时，自发偏好就消失了（实验 2）。最后，结果表明，全局配置的方向本身并不是决定新生儿偏好的关键因素（实验 3）。这些结果表明，人类对重力方向具有天生的倾向，这种倾向会影响生物运动的感知，并支持这样一种假设，即在视觉经验之前，已经有一个用于检测生物运动的机制在起作用。
